In the field of packing techniques, it is known from prior use that for an in-line production of plastic bags made of an endless film and containing stacked soft hygienic products a stack forming unit for bundling product items to a stack is provided. By means of a stack transport unit the formed stack is supplied to a wrapping station. The latter comprises a supply tunnel through which the formed stacks are delivered to the wrapping station in a row. To pack the incoming stacks a polymer film is used which is supplied by means of a film feed unit from the film stock, like a film roll.
To wrap the film web around the stacks, a funnel-shaped forming shoulder arranged around the supply tunnel is provided, which has a substantially rectangular cross section design. The fed film is drawn over this forming shoulder and guided onto the supply tunnel forming a tube-like film envelope around the stacks leaving the supply tunnel. Usually, the funnel-shaped forming shoulder shows a symmetric design so that the longitudinally running edges of the tube-like film envelope around the stacks are located in the centerline of one of the side faces of the bag. Accordingly, a machine direction (abbreviated “MD” in the following) sealing unit seals these longitudinally—running edges thus leading to a plastic weld seam on the associated side face of the bag.
Finally, to complete the plastic bag around one stack of hygienic products a cross direction (abbreviated “CD” in the following) sealing unit is used for forming and sealing the crosswise running edges of the tube-like film envelope for each plastic bag, simultaneously separating the sequenced bags.
Due to the side face centered weld seam applied by the MD sealing unit, this side face is lost for any imprint fully covering this side face without being disturbed by the weld seam.
WO97/20737 discloses method and apparatus for feeding resiliently compressed articles to a form/fill/seal machine.
Plastic bags for feminine hygiene articles having one single MD seal along one corner of the bag have been sold in Asia. However it is believed that these bags have been produced using a process wherein the plastic film used has been pre-sealed in the MD direction and folded at least once before being fed into the packing line. A folding line in the center of a side panel is therefore visible in these finished plastic bags.
It is an object of the invention to simplify the production of plastic bags containing stacked soft hygienic products. It is another object of the invention to provide an improved packaging device for packing stacked soft hygienic products by means of plastic bags comprising four completely printable side faces in the MD direction.